Method for improving the mechanical and hydraulic characteristics of foundation grounds of existing built structures

ABSTRACT

A method for improving the mechanical and hydraulic characteristics of foundation grounds of existing built structures, includes the following steps:
         a first step of two-dimensional or three-dimensional sensing of at least one portion of the built structure;   a step of identifying at least one region of intervention in the foundation ground beneath the at least one portion sensed in the first sensing step; and   a step of injecting, through holes provided at least at a part of the intervention region, a cement or synthetic mix. The method further includes   second steps of two-dimensional or three-dimensional sensing, mutually spaced in time, of the at least one portion during the injection step; and   a step of interrupting the injection step on the basis of the information gathered during second steps of two-dimensional or three-dimensional sensing of the at least one portion.

TECHNICAL FIELD

The present disclosure relates to a method for improving the mechanicaland hydraulic characteristics of foundation grounds of existing builtstructures.

BACKGROUND

Any built structure transmits to the ground pressures that produce inthe ground deformations deferred over time, known as subsidences. Whenthe subsidences are different at the base of two points of the samebuilt structure, the difference between the measured values is termeddifferential subsidence.

Structural engineering indicates the extent of the differentialsubsidences that can be tolerated by different types of builtstructures.

Geotechnical engineering provides reliable calculation methods suitableto estimate differential subsidences during design.

Usually, differential subsidences of the ground at the base of existingbuilt structures are scarcely significant and do not cause deformationsof the structure such as to bring out damage, collapses or malfunctionsin general.

However, there are cases in which the differential subsidences of theground cause displacements of the overlying built structure that exceedthe allowable tolerances and are such as to cause failures on thestructure which are often not negligible. Reference is intended to casesin which the ground is particularly deformable with respect to thepressures transmitted by the built structures or to cases in which thebuilt structures are not adequate.

Therefore, two approaches for the solution of differential subsidencesare distinguished: the intervention aimed at preventing the onset ofdifferential subsidences on built structures during design or onexisting built structures that are being extended or converted, andinterventions aimed at solving differential subsidences that havealready occurred on existing built structures. The method usually usedto prevent the forming of differential subsidences on a built structureundergoing construction design provides for adapting the geometry andrigidity of the foundations to the load bearing characteristics of theground or, in the more complex case of existing built structures, forwhich extension or conversion work is planned, provides for comparisonbetween the mechanical characteristics of the ground and the additionalloads produced by the work for extension or conversion that the existingfoundations transmit to the ground.

The method usually used to deal with differential subsidences that haveoccurred on existing built structures is more complex than the precedingone and provides for a double analysis that relates to the foundationground and to the structure of the built structure.

The first one assesses the nature and consistency of the ground in thevolume in which the differential subsidence has occurred andconsequently allows to calculate the resistance and deformability withrespect to the loads of the built structure.

The second one reconstructs in details the differential motions of thestructure that have generated the cracks that are present on the builtstructure both in terms of time and in geometric terms.

For ground analysis, the designer can employ traditional geotechnicaltests both in situ and in the laboratory. The ground analysis methodsubstantially derives from traditional geotechnics and provides forcalculating the resistance and deformability of the soil that is presentbelow the various portions of the built structure starting from thegeotechnical parameters obtained from the tests.

The analysis of the built structure, in addition to providing anaccurate assessment of the loads according to the faithfulreconstruction of the nature of the materials used and an interpretationof the cracking situation that is present on the masonry, is based onmeasurements of displacements and deformations by means of instrumentslinked to topography and structural monitoring. Leveling operations withprecision instruments are performed often in order to check which partof the built structure has subsided and the extent of the displacement.Topographic readings are then combined with monitoring operations bymeans of tell-tales, inclinometers, strain gauges, etc., which have thetask of checking whether the subsidence is evolving and at what rate itis developing.

After completing the analysis on the foundation ground and on thestructure of the built structure, the designer defines the most suitablemethod for preventing or solving differential subsidences.

There are various systems for preventing or solving differentialsubsidences.

In particular, a distinction is made between systems that act on thestructure and systems that treat the ground.

The former have the task of modifying the manner in which the pressuresof the built structure are transferred to the ground by means of workintended to widen the base of the foundation or to extend it deeper intothe ground until it encounters more substantial and therefore strongerlayers. For this reason, the described methods are usually applied tothe entire structure: among these, mention is made for example ofmicropiles and sub-foundations.

The latter have the task of improving the strength and deformabilitycharacteristics of the ground by means of actions aimed at increasingthe density of the mass and or at introducing therein materials or mixesthat modify physically or chemically the characteristics of the naturalground. These methods can be limited to some portions of the builtstructure, where the ground has poorer characteristics. This categoryincludes, among others, injections of concrete and synthetic resins.

As specified in the UNI EN 12715 standard, EXECUTION OF SPECIALGEOTECHNICAL WORK—GROUTING, the injections are distinguished mainly intotwo categories: injections that do not produce ground displacement andinjections that produce ground displacement.

Injections that do not produce ground displacement are limited toalluvial grounds up to a certain value of particle size fineness and areperformed by simple permeation.

The parameters that regulate the injectability of a ground by simplepermeation are the permeability coefficient of the ground proper and theaverage diameter of the particles that constitute the mix. The chart ofFIG. 4 shows the borderline for injections by simple permeation(low-pressure injections), to the left of which ground displacementoccurs necessarily.

With low-pressure injections, the mixes tend to fill the interconnectingpores of the ground, without causing hydro-fracturing (or claquage)phenomena that are responsible for significant volume variations of theground.

During an injection process that does not produce ground displacement,the maximum pressures applied by the pumping systems and/or the maximumexpansion pressures of the mixes must therefore remain below a criticalvalue defined by the term P_(crack)[kPa]. This value depends on manyfactors, including the weight and the mechanical characteristics of theground that lies above the injected volume. From a theoreticalstandpoint, the expression of P_(crack)[kPa] is as follows:

P _(crack)[kPa]=(γ′*z*v)*(1+sin φ)+c

-   -   γ′=weight of immersed volume of the ground;    -   z=depth to which injection is performed with respect to the        plane of site;    -   v=Poisson coefficient;    -   φ=angle of shear strength of the ground;    -   c=ground cohesion

The theoretical value of P_(crack)[kPa] is then validated in the varioussites by means of preliminary injectability tests.

During an injection process that does not produce ground displacement,the pressures must increase gradually, since the progressivelyincreasing presence of the mix or of the synthetic resin in the groundtends to reduce intergranular flow spaces.

The increase proceeds until the pressure P_(crack)[kPa] is reached whichdetermines a displacement of the ground and/or of the overlying builtstructure.

The field of application of this type of injection is limited to highlypermeable and uniform grounds and the method requires very long times.

Among the various known methods for solving differential subsidences bymeans of injections that do not produce ground displacements, mention ismade for example of the TMG (Trevi Multi Grouting) method applied by theTrevi company, which uses for each perforation a bundle of single-valvepipes that are connected selectively to a plurality of pumps with verylow flow-rates and pressures.

The main limitation of this type of technology resides in that in theabsence of systems for sensing the overlying structure as describedabove, reaching the pressure P_(crack)[kPa] is avoided intentionally,limiting the effectiveness of the intervention.

The injections in fact are usually stopped when a previously determinedinjection pressure is reached or by injecting a mix with a limitedexpansion pressure.

These pressures are far lower than the pressure P_(crack)[kPa], whilethe effectiveness of the intervention is maximum indeed when thepressure is increased gradually to the vicinity of this value.

Another limitation of this type of injection is that the injected mixescan drift away from the desired point and reach less confined regions,where the weight and the characteristics of the overlying soil aredifferent, to the point of causing unwanted displacements of the groundor of the structure in regions of the built structure that are far fromthe volume of ground that one intends to treat.

All other types of injection of mixes in foundation grounds, which arenot permeation only, necessarily generate differential displacements inthe overlying structure, which are caused by the injection pressureproduced by the pump or by the expansion pressure of the mix.

Among the various known methods for solving differential subsidences bymeans of injections that produce ground displacements, mention is madefor example of the method disclosed in EP0851064, which provides for anincrease in the load-bearing capacity of foundation grounds forbuildings, by means of the injection of a substance that expands as aconsequence of a chemical reaction. The disclosed method uses laserreceivers that are fixed to some points of the built structure that liesabove the injected volume and which, connected to an emitter, indicatethe vertical displacements of the built structure as a consequence ofthe expansion of the substance in the ground.

There are other methods that provide for the injection of mixes of adifferent kind which cause ground displacement. Among these, mention ismade of the Soilfrac technology of the Keller company, which providesfor the use of cement mixes, including expanding ones. The methodprovides for the creation in multiple steps of fractures in the groundon the part of the mix injected by means of a pump that generatesmedium-high pressures. In this case also, monitoring of thedisplacements of the overlying building is provided by means of levelmeter systems that allow to observe the relative displacement of somepoints of the built structure with respect to others, utilizing theprinciple of communicating vessels.

Therefore, in known methods, which provide for injections that produceground displacement, during work some points of the built structure onwhich the laser receivers or the level meter cups or other systems,which are in any case localized, may undergo a worsening of the crackingsituation due to excessive differential displacements of some portionsof the structure, such as to represent a risk for the entire builtstructure and without a clear awareness of the phenomenon on the part ofthose who perform the work.

In known cases, in fact, monitoring of the displacements of the builtstructure during the injection step is performed in a localized manner,usually by means of a laser level or level meter chains, which measurevertical or relative displacement between points.

One of the best-known methods for checking the effectiveness of aninjection intervention relates to observing an initial rise of theportion of built structure that lies above the injection point. Theinitial rise of the structure bears witness to the fact that themechanical and hydraulic characteristics of the ground have beenincreased, since the injected ground not only withstands the pressureinduced by the overlying load but also withstands the dynamic pressuresthat are generated upon lifting.

By following this type of verification, in known methods that providefor injections that produce ground displacement, during work themonitoring systems may be anchored to portions of the structure that arenot loaded, for example portions of the structure located on builtstructure portions located beneath wall damage. In such cases, theoperator, by observing a displacement of the built structure by means ofthe localized monitoring system (optical level; laser level, level metersystem; etc.), decides to end the injection process before the portionof structure that lies above the injection has actually moved andtherefore before the injection has produced a sufficient improvement ofthe characteristics of the conditions of the foundation ground.

In particular, the method disclosed in EP0851064 provides for eachindividual injection of synthetic mix to be interrupted when adisplacement of the overlying structure is detected. During work, thedisplacements detected at each injection are added and can producedisplacements that cannot be withstood by the structure. It might alsobe indispensable to interrupt the work before the entire portionintended has been treated, in order to avoid damage to the structure.

In known methods, moreover, the displacements are measured along asingle direction and displacements in the other directions are notdetected. Therefore, the injection process may produce unwantedmovements that damage the structure, following directions that are notmonitored by the sensing systems.

SUMMARY

The aim of the present disclosure is to solve the problems describedabove, by providing a method that is capable of providing criteria forverifying the increase of the mechanical and hydraulic characteristicsof the ground and of preserving the built structure against excessivedistortions that might be produced during execution of work adapted tosolve differential subsidences.

Within this aim, the present disclosure provides a method thatintegrates or replaces localized monitoring systems.

The present disclosure also provides a method that is simple and quickto perform.

These advantages are achieved by providing a method including thefollowing steps a first step of two-dimensional or three-dimensionalsensing of at least one portion of the built structure; a step ofidentifying at least one region of intervention in the foundation groundbeneath said at least one portion sensed in said first sensing step; astep of injecting, through a plurality of holes provided at least at apart of said intervention region, a cement or synthetic mix; secondsteps of two-dimensional or three-dimensional sensing, mutually spacedin time, of said at least one portion during said injection step; and astep of interrupting said injection step on the basis of the informationgathered during second steps of two-dimensional or three-dimensionalsensing of said at least one portion.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the present disclosure willbecome better apparent from the description of some preferred but notexclusive embodiments of the method according to the disclosure,illustrated only by way of nonlimiting example in the accompanyingdrawings, wherein:

FIG. 1 is a schematic view of a built structure on which work isnecessary;

FIG. 2 is a schematic view of the first sensing step;

FIG. 3 is a schematic view of the injection step and of the secondsensing steps; and

FIG. 4 is a chart related to the injectability of the grounds as afunction of the properties of the mix and of the ground.

DETAILED DESCRIPTION OF THE DRAWINGS

With reference to FIGS. 1-4, the present disclosure relates to a methodfor improving the mechanical and hydraulic characteristics of foundationgrounds of existing built structures.

The method comprises:

-   -   a first step of two-dimensional or three-dimensional sensing of        at least one portion 2 of the built structure 1;    -   a step of identifying at least one region of intervention 3 in        the foundation ground beneath the at least one portion 2 sensed        in the first sensing step;    -   a step of injecting, through a plurality of holes 4 provided at        least at a part of the intervention region 3, a cement or        synthetic mix;    -   second steps of two-dimensional or three-dimensional sensing,        mutually spaced in time, of the at least one portion 2 during        the injection step.

In particular, there is a step of interrupting the injection step on thebasis of the information gathered during the second steps oftwo-dimensional or three-dimensional sensing of the at least one portion2.

In greater detail, the step of interrupting the injection step isperformed if the two-dimensional or three-dimensional sensing of the atleast one portion 2 sensed in the second sensing steps finds, betweentwo successive sensings, as a function of the intervention type:

a. an overall displacement of at least one part of the at least oneportion 2 that lies above the intervention region 3; or

b. a differential movement of parts of the at least one portion 2 thatsubstantially corresponds to the limit of allowable deformation of theat least one portion 2; or

c. the reaching, on the part of the portion that lies above theintervention region 3 of the built structure 1, of a position that waspredefined during design.

Conveniently, the portion 2 comprises at least one part of a building orof a built structure, such as for example a vertical wall, a face or afloor.

Preferably, the first sensing step and/or the second sensing steps areperformed by using at least one device for the optical acquisition ofthe two-dimensional or three-dimensional portion.

Advantageously, the acquired images are of the digital type.

Preferably, the optical acquisition device 20 comprises a 3D laserscanning device, which, placed at a suitable distance from the builtstructure, is capable of emitting laser beams along all directions andof obtaining the exact position of a cloud of points that lie on thebuilt structure being considered.

The data thus acquired can be displayed in real time on the deviceproper or also on a computer, so that they can be examined more easily.

The first sensing step is adapted to sense two-dimensionally orthree-dimensionally a portion from the outside or from the inside of thebuilding.

The second sensing steps are adapted to detect two-dimensionally orthree-dimensionally a portion from the outside or from the inside of thebuilding.

Conveniently, the first sensing step and/or the second sensing stepsubstantially relate to placing the optical acquisition device 20, whichcomprises for example a laser scanning device such as a 3D scanner laserdetector, in the vicinity of the building, in a point that allows tosense the entire face or a part thereof (or part of the floor) belowwhich the steps of injection in the ground of cement or synthetic mixeswill be performed.

Nothing prevents the first sensing step and/or the second sensing stepsfrom being performed by other types of sensing devices.

By way of example, it has been found that it is particularly effectiveto perform the first sensing step and/or the second sensing steps bymeans of a radar device.

Conveniently, the radar device is of the interferometer type.

It is further possible to provide for the first sensing step and/or thesecond sensing steps to be performed by a device for emitting/receivingelectromagnetic waves and/or acoustic waves or by similar devices.

The first sensing step can provide for one or more scans of the builtstructure to determine the exact position, and specifically of theintervention region 3, prior to the beginning of the injection step.

The method continues with the provision of a plurality of holes in theground beneath the intervention region 3, even through the foundation ofthe built structure.

Typically, the diameter of the holes varies between 6 mm and 200 mm.

The depth of the holes is a function of the dimensions of the foundationground and their center distance is usually comprised between 0.50 m and3.0 m.

Pipes are then accommodated in the holes and the cement or syntheticmixes are injected into the ground through such pipes.

The non-expanding mixes or synthetic resins are injected into the groundby means of pressure pumping systems, which force the entry of the mixesor synthetic resins in the intergranular voids or, in the presence ofgrounds having a finer texture, produce hydro-fracturing, i.e., localbreakup of the ground and the forming of lattices of mix which, onceset, improve the mechanical characteristics of the mass. The pumpingsystems for the non-expanding mixes or synthetic resins deliverflow-rates on the order of 5-30 liters per minute and usually generatepressures comprised between 10 and 30 bars.

These pressures are capable of forcing the penetration of the cement orsynthetic mixes in the intergranular voids of sandy and gravelly groundsand to allow access of the cement or synthetic mix in silty or clayeygrounds by means of local ruptures known as hydro-fractures.

The non-expanding mixes or synthetic resins, moreover, can be injectedinto the ground by means of high- or very high-pressure pumping systems(200 bar to 400 bar), which break up the ground in place and allow thestirring of the matrix with the mix. This last system is known as jetgrouting.

The expanding synthetic or cement mixes are injected into the groundthrough low-pressure pumping systems.

The penetration of the cement or synthetic mixes in the intergranularvoids of coarse grounds or the hydro-fracturing of grounds having afiner texture occurs by means of the pressure that is generated duringthe expansion step, which usually occurs by chemical reaction, reachingvalues comprised between 0.5 bar and 150 bar.

In the presence of grounds having a finer texture, the hydro-fracturingprocess is produced not only by the injection pressure but also by theexpansion pressure of the cement or synthetic mix. Subsequent hardeningof the mix diffused in the ground produces the improvement of thegeotechnical characteristics.

In all of the cases cited above, both by pumping into the ground underpressure non-expanding synthetic or cement mixes and by pumping into theground at low pressure expanding synthetic or cement mixes, inevitablythe injection treatment produces a significant volume variation of theground.

This significant volume variation of the ground produces a displacementof the adjacent and overlying volumes of ground that have not beeninjected, which, as the injection proceeds, necessarily entail evidentdisplacements of the overlying built structure and therefore of theintervention region 3. The pressure generated in the ground by theinjection process, be it performed by means of non-expanding syntheticor cement mixes or by means of expanding synthetic or cement mixes,exceeds the pressures transmitted to the ground by the built structure.

For this reason, during the entire injection step one proceeds with thesecond sensing steps (two-dimensional or three-dimensional scanning) ofthe entire built structure or a portion thereof.

The second sensing steps repeated during the injection step provideoperators with a complete picture of the built structure and indicate inreal time any critical regions that might generate angular distortionsthat are not allowable for the structure.

This monitoring system, in addition to providing information regardingsafety against displacements of the structure during the injection step,is used to return indications as to the overall response of the builtstructure and therefore the effectiveness of the step of injection intothe ground.

With the introduction of the first sensing step and of the secondsensing steps by means of the device 20 for two-dimensional orthree-dimensional optical acquisition of the portion (for example bymeans of a 3D scanner laser monitoring device, or by means of a radardevice or the like), the function of controlling the effectiveness ofthe injection, typically performed by traditional laser monitoringtopographic systems, as disclosed extensively in EP 0851064, improvessignificantly, since it does not merely monitor some points of thestructure but it extends the observation to a two-dimensional orthree-dimensional portion of the built structure.

The injection step proceeds until the device 20 for optical acquisition(by radar or by means of similar devices) provides indications of aglobal displacement of the portion 2 of built structure that lies abovethe intervention region 3 that is detectable but as small as desired (adisplacement on the order of magnitude of the tolerance of theinstrument used). In this manner one of the best-known criteria forverifying the effectiveness of an intervention for injection into theground is upheld.

For example, the displacement is global when it affects a certain numberof points (from a few tens to several thousand) that are distributedpreferably evenly on the portion of built structure that is the subjectof the intervention.

If necessary, as an alternative, the injection step can proceed beyondthe minimal global displacement and can produce the lifting or ingeneral the displacement of the built structure.

There is a second category of interventions for which injection proceedsuntil the optical acquisition device 20 detects on any portion of thebuilt structure the forming of angular distortions that are proximate tothe allowable tolerances for the structure.

The angular distortions are defined as the ratio between thedifferential vertical displacement between two points of the same builtstructure (differential subsidences or differential rise) and theirminimum distance. The person skilled in the art is always capable ofdetermining the allowable tolerances with the aid for example of tablesthat list the allowable values and the limit values for the angulardistortions as a function of the type of building. By way ofnonexhaustive example, the most significant are given hereafter:

Limiting angular distortions according to Bjerrum (1963) Category ofpotential damage tanß Limit beyond which problems can arise in machinesthat are 1/750 sensitive to subsidences Danger limit for latticestructures 1/600 Safety limit for buildings in which no cracking isallowed 1/500 First cracking in panel walls and difficulty in usingbridge cranes 1/300 Limit beyond which tilting of tall buildings can bevisible 1/250 Considerable cracks in panel walls and load-bearing brickwalls 1/150 Safety limit for load-bearing brick walls with h/L < ¼ 1/150Limit beyond which structural damage to the buildings is to be 1/150feared

Allowable angular distortions according to Sowers (1962) Type ofstructure tanß Multistory load-bearing masonry 0.0005 ÷ 0.001Single-story load-bearing masonry 0.001 ÷ 0.02 Damage to plasters 0.001Reinforced concrete frames 0.0025 ÷ 0.004 Walls of structures withreinforced 0.003 concrete frame Steel frames 0.002 Simple steelstructures 0.005

The allowable values of the angular distortions for the built structurebeing studied are defined during design.

Finally, a third category of possible interventions which isintermediate between the two described earlier is pointed out in whichinjection might be interrupted when the portion of built structure thatlies above the intervention region 3 reaches a position that has beenpredefined during design.

This is the case of lightweight built structures, such as flooring orroads, which do not offer a sufficient contrast to the injectionpressure or to the expansion pressure of the cement or synthetic mixes.In most of these cases, the overall displacement of the built structureportion that lies above the intervention region may be insufficient toverify the effectiveness of the intervention and it is thereforepreferable to determine during design the desired displacement as afunction of the characteristics of the ground and of the builtstructure.

Another example of intervention that lies within this category relatesto industrial or civil flooring that has significant hollows, such as toprevent its normal use. The design in this case might provide for thelocal lifting of the flooring to a level that is deemed sufficient toregain its planarity but in any case much higher than the tolerance ofthe sensing instrument used (for example on the order of centimeters),while remaining well below the limit of allowable deformation of suchflooring.

Other examples of interventions that lie within this category relate tohistorical buildings or built structures that are close to collapse andcannot tolerate significant displacements and for which the injectionsare sized appropriately in terms of quantity of mix to be injected andin terms of injection pressures. Or very heavy buildings for which thesensing of an overall displacement, especially with the firstinjections, might require quantities of cement or synthetic mixes thatexceed those strictly necessary in order to improve the mechanical andhydraulic characteristics of the ground.

In these cases, the injection step is interrupted upon reachingpredefined quantities of mix during design although the above citedcriterion of effectiveness has not been upheld in every injection point.

If the design requires that the built structure must not undergosignificant displacements, the injections will be interrupted when thedisplacement sensing system detects a minimal displacement, on the orderof instrument precision, even in a single point of the built structure.

The injection step can also be performed by using alternately or insuccession mixes of different types.

For example, in order to reduce the costs of the intervention, theremight be a first step of injection of cement mixes followed by theinjection of synthetic mixes.

Otherwise, if the foundation ground has nonuniformities in theintervention region, different types of synthetic mix might be used inorder to optimize consumptions and the obtained results.

The injection step can also be performed by using simultaneously aplurality of injection pumps. In this case, the injections can beperformed by limiting the angular distortions that are induced on thestructure, allowing the injection of more cement or synthetic mix beforethe limit of allowable deformation is reached, thus achieving a betterresult.

In practice it has been found that the method according to thedisclosure achieves fully the intended aim, since it allows, in asimple, quick, effective and final manner to preserve the builtstructure against excessive distortions that might be produced duringexecution of work for improving the mechanical and hydrauliccharacteristics of the grounds, replacing or integrating spot monitoringsystems with a system for two-dimensional or three-dimensionalmonitoring of portions of the building.

The disclosures in Italian Patent Applications No. 102015000035300(UB2015A002280) and No. 102016000017692 (UB2016A000937) from which thisapplication claims priority are incorporated herein by reference.

1-12. (canceled)
 13. A method for improving the mechanical and hydrauliccharacteristics of foundation grounds of existing built structures, themethod including the following steps: a first step of two-dimensional orthree-dimensional sensing of at least one portion of the builtstructure; a step of identifying at least one region of intervention inthe foundation ground beneath said at least one portion sensed in saidfirst sensing step; a step of injecting, through a plurality of holesprovided at least at a part of said intervention region, a cement orsynthetic mix; second steps of two-dimensional or three-dimensionalsensing, mutually spaced in time, of said at least one portion duringsaid injection step; and a step of interrupting said injection step onthe basis of the information gathered during second steps oftwo-dimensional or three-dimensional sensing of said at least oneportion.
 14. The method according to claim 13, wherein said step ofinterrupting said injection step is performed if the two-dimensional orthree-dimensional sensing of said at least one portion sensed in saidsecond sensing steps reveals, between two successive sensings, as afunction of the intervention type: a. an overall displacement of atleast one part of said at least one portion that lies above saidintervention region; or b. a differential displacement of parts of theat least one portion that substantially corresponds to the allowabledeformation limit of the at least one portion; or c. the reaching, onthe part of the portion that lies above the intervention region, of aposition that was predefined during design.
 15. The method according toclaim 13, wherein said at least one portion comprises at least one partof a floor structure.
 16. The method according to claim 13, wherein thatsaid at least one portion comprises at least one part of a verticalwall.
 17. The method according to claim 13, wherein said at least oneportion comprises at least one part of a building.
 18. The methodaccording to claim 13, wherein said first sensing step or said secondsensing steps are performed by at least one optical acquisition device.19. The method according to claim 18, wherein said optical acquisitiondevice comprises a laser scanning device.
 20. The method according toclaim 13, wherein said first sensing step or said second sensing stepsare performed by a radar device.
 21. The method according to claim 20,wherein said radar device is of the interferometry type.
 22. The methodaccording to claim 13, wherein said first sensing step and/or saidsecond sensing steps are performed by a device that emits/receiveselectromagnetic and/or acoustic waves.
 23. The method according to claim13, wherein said first sensing step and/or said second sensing steps areadapted to sense a portion from the outside or from the inside of saidbuilding.
 24. The method according to claim 13, wherein said injectionstep is not limited to permeation only.